Satellite-based radio navigation systems are known and are capable of broadcasting continuous position, velocity, and time information to an unlimited number of users. One such system is currently in place in the United States and is known as the NAVSTAR (NAVigation Satellite Timing And Ranging) Global Positioning System (GPS). GPS is an absolute positioning system capable of providing accurate three-dimensional position and time-at-position information. Presently, the GPS includes 24 satellites uniformly disbursed about six orbital planes of four satellites each. Each of the orbits are included at an angle of 55 degrees relative to the equator and are separated from each other by multiples of 60 degrees longitude. The orbits have an orbital radii of 26,560 kilometers (which translates to an altitude of approximately 11,000 nautical miles), and are approximately circular. The orbits are non-geo-synchronous, with 0.5 sidereal day (11.967 hours) orbital time intervals, so that the satellites move with time relative to the earth. Further, each satellite has an atomic clock synchronized system-wide to provide for highly accurate time clock information such as time-of-day and calendar date. This design ensures that signals from at least four GPS satellites can be received at any point on or above the earth's surface at any point in time. A discussion of GPS technology and applications thereof is given in Harris and Sikorski, GPS Technology and Opportunities, presented at Expo Comm. China '92, Bejing, China, Oct. 30-Nov. 4, 1992.
Another satellite navigation system, known as GLONASS (GLObal Orbiting NAvigation Satellite System), operates similarly to GPS and is currently in place over Russia. GLONASS also uses 24 satellites which are distributed approximately uniformly in three orbital planes of eight satellites each. Each orbital plane is inclined at 64.8 degrees relative to the equator, and each of the three orbital planes are offset from each other by multiples of 1200 longitude. The GLONASS orbits are smaller and shorter than their US counterparts, having radii of approximately 25,510 kilometers and periods of 8/17 of a sidereal day (11.26 hours) respectively.
The use of satellite navigation systems for determining the global position of an observer is known as exemplified by U.S. Pat. No. 5,434,787 to Okamoto et al. and U.S. Pat. No. 5,434,789 to Fraker et al. Further, it is known to utilize a satellite navigation system to determine the global position of an observer while using a separate time-keeping device to determine time-at-position information. Examples of such systems are given by U.S. Pat. No. 5,490,079 to Sharpe et al., U.S. Pat. No. 5,488,558 to Ohki, and U.S. Pat. No. 5,398,190 to Wortham. Further yet, it is known to utilize a satellite navigation system to determine both the global position and time-at-position of an observer, as exemplified by U.S. Pat. No. 5,479,351 to Woo et al., U.S. Pat. No. 5,311,197 to Sorden et al and U.S. Pat. No. 5,262,774 to Kuwahara et al.
While some of the foregoing systems are operable to provide position and time-at-position information of an observer, each of these systems suffers from undesirable drawbacks. For example, none of the foregoing systems are operable to log several instances such position and time-at-position information and provide such information to a data reporting arrangement. Further, none of the foregoing systems is programmable to operate in either a manual or automatic mode. Further yet, none of these systems may be programmed for operation from a remote location. Still further, none of these systems is operable to log such information in response to an automatic external event which may be programmed at any time from a remote location. What is therefore needed is a position and time-at-position logging apparatus and system incorporating, inter alia, some of the foregoing features lacking from known position and time-at-position determining apparatuses.